import math
x1, y1, x2, y2=map(float,input().split())

x=x1-x2
y=y1-y2

h=x**2+y**2

print(h**0.5) import math math x1, y1, x2, y2=map(float,input().split()) x1 map(float,input().split()) map float input().split() ().split () input split y1 x2 y2 x=x1-x2 x x1-x2 x1 x2 y=y1-y2 y y1-y2 y1 y2 h=x**2+y**2 h x**2+y**2 x**2 x 2 y**2 y 2 print(h**0.5) print h**0.5 h 0.5 x1, y1, x2, y2=map(float,input().split()) map(float,input().split()) x1 x2, y2=map(float,input().split()) map(float,input().split()) x2 x=x1-x2 x1-x2 x h=x**2+y**2 x**2+y**2 h y=y1-y2 y1-y2 y y2=map(float,input().split()) map(float,input().split()) y2 y1, x2, y2=map(float,input().split()) map(float,input().split()) y1
import math
x1, y1, x2, y2=map(float,input().split())

x=x1-x2
y=y1-y2

h=x**2+y**2

print(h**0.5)
